Android Studio Java Files

Ok so when i try to import something into the java files it disappears about two seconds later, i had this problem before so i deleted android studios and everything downloaded with the sdk and deleted the jdk, finaly after re-installing EVERYTHING it sesmed to be working than suddenly about a half hour later i got the same problem this is so angering someones's help will be appreciated. https://www.youtube.com/watch?v=T-W-o_WSUag&feature=youtu.be Here is a short video to what is happening